Imidazole type curing agents and latent systems containing them

Abstract

The disclosed curing agents or initiators have the formula ML n (O-SO 2 -R f ) m wherein L is an imidazole, M is a metal, n is a coordination number of M, R f is a fluorinated alkyl group, and m is the valence of M. These curing agents are useful in latent curable epoxy systems. Upon heating to the cure temperature (e.g. 100° - 250° C.), such systems cure efficiently and with a low exotherm.

What is claimed is: 
     
       1. A latent reactive system which reacts at temperatures above 50° C. comprising a first compound containing the 1,2 epoxy group and a second compound of the formula   ML.sub.n (O--SO.sub.2 --R.sub.f).sub.m     wherein   L is selected from the group consisting of imidazole and halogen or hydrocarbon derivatives thereof,   M is a metal selected from Groups VIII, IB, and IIB, of the Periodic Table,   n is a coordination number of M,   R f  is a fluorinated alkyl group of 1-18 carbon atoms, and   m is the valence of M.   
     
     
       2. A system according to claim 1 wherein said compound containing the 1,2 epoxy group is an epoxide selected from the group consisting of a polyglycidyl ether of a polyhydric phenol and a cycloaliphatic epoxide. 
     
     
       3. A system according to claim 1 wherein n is a number from 2 to 6 and M is a metal selected from the group consisting of iron, cobalt, nickel, copper, cadmium, zinc and silver. 
     
     
       4. A system according to claim 1 wherein L is benzimidazole. 
     
     
       5. A latent reactive system according to claim 1 wherein said second compound is a compound of the formula   ML.sub.n (O--SO.sub.2 --R.sub.f).sub.m     wherein   M is a metal selected from Groups VIII, IB and IIB of the Periodic table,   n is a coordination number of M ranging from 2 to 8,   R f  is a fluorinated alkyl or cycloalkyl group of 1 to 18 carbon atoms wherein the carbon atom alpha to the sulfonyl radical has the non-sulfur valence bonds taken up by fluorine atoms or fluorinated alkyl or cycloalkyl substituents,   m is the valence of M, and   L is an imidazole of the formula ##STR5## wherein R 1 , R 2 , R 3  and R 4  are the same or different and are selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, alkaryl and arylalkyl, said alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, alkaryl and arylalkyl having from 1 to 15 carbon atoms, wherein R 1  and R 2  can together, and with the ring carbon atoms of the imidazole nucleus to which they are shown attached, form a fused carbocyclic ring having 5 or 6 ring carbon atoms, and wherein R, or R 2  can together with R 3 , and with the ring carbon and nitrogen atoms of the imidazole nucleus to which they are shown attached, form a fused N-heterocyclic ring.   
     
     
       6. A method of curing the latent reactive system of claim 1 comprising the step of heating said system to a cure temperature in the range of 100° -250° C.